Theoretical and experimental insights into electron-induced efficient defluorination of perfluorooctanoic acid and perfluorooctane sulfonate by mesoporous plasma

Abstract Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) are global environmental pollutants and pose significant threats to environmental safety and human health. Defluorination of PFOA and PFOS was investigated theoretically and practically in a mesoporous plasma system in this study. Rapid and highly efficient defluorination was realized, and 98% and 65% defluorination rate for PFOA and PFOS, respectively, were obtained within 60 min of treatment. Electrons generated in the mesoporous plasma system played a decisive role in PFOA and PFOS defluorination; other species, including 1O2 and ·OH, also contributed to defluorination. C-F, C-C, and C-S bonds were broken by plasma oxidation; various shorter-chain perfluorocarboxylic acids, polyfluoroalkyl substances, and alcohols were produced. PFOA and PFOS decomposition mechanisms involved electron transfer, defluorination, decarboxylation, and hydroxylation reactions. Desulfonation reactions were also involved in PFOS decomposition. Density functional theory calculations identified sites susceptible to be attacked and the main degradation pathways. Effective defluorination of PFOA and PFOS reduced their toxicities. Furthermore, its potential for actual surface water treatment was also determined.